Do you feel underground tunnels below cities are "caving" ? I know a few people who do this. Some are old and unused from decades ago. Illegal. But they still do it. They're like, "I went in here, and ended up in this side of the city way far away".

Not technically "caving" (caves are natural, not man-made), but exploring tunnels and disused mines etc is popular with some cavers too. New York City has lots of abandoned tunnels and aqueducts for the intrepid urban explorer. Or so I hear.

I still recall as a child of about 11 or 12 exploring the drain tunnels underneath the sprawling metropolis of Hattiesburg, MS. This was well before I ever actually did any real caving, but it was quite an adventure for me and my friends, hiding out and smoking cigarettes away from the prying eyes of civilization. I wonder now if this was not an early manifestation of the caving obsession that I only discovered later in life.

Cleveland Grotto has, for decades, been a leader in "sewering" as we call it. As noted, NYC and other towns have extensive systems. Paris, France is another. In the post-911 world it has become a bit problematic in our area to do much sewering. However, it used to be the go-to event when a visiting cave dignitary came to town as Cleveland has few caves of any size.